2-ethynyl-l,3-amino alcohols

The InI-Pd(0)-promoted allylation of aldehydes with N-activated vinylaziridines or allylic acetates proceeds with regio- and stereoselectivity, irrespective of the chirality of the allylic carbon bearing the vinyl group, to provide sy ,syn-2-vinyl-l,3-amino alcohols with three contiguous chiral centers (Scheme 8.64) [90]. In a similar manner, 2-ethynyl-l,3-amino alcohols are synthesized from 2-ethynylaziridines (Scheme 8.65) [91]. 

In order to synthesize alkyne 223, enantioenriched ethynylaziridme 220 was prepared by a known four-step sequence (762) from (S)-Gamer s aldehyde (765,164). A reductive coupling reaction (765,166) of the aziridine 220 with formaldehyde in the presence of Pd(Ph3)4 and Inl furnished the 2-ethynyl-l,3-amino alcohol 221. Protection of 221 as benzylidene acetal gave the alkyne 222, which was converted in the next step to the corresponding iodoalkyne 223 (767). 

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